Sampling and counting system

Abstract

A system for testing the efficiency of a test HEPA filter, the system comprises a dilution system and a sampling system. The dilution system processes samples collected upstream of the test HEPA filter. The dilution system has a test portion and a calibrated portion. The calibrated portion aids in determining the dilution ratio of the test portion thereby rendering the dilution system self-calibrating. The sampling system receives upstream samples via the dilution system, and downstream samples collected directly downstream of the test HEPA filter. The sampling system incorporates a flow rate balancing system to ensure accurate counts with respect to samples collected upstream and downstream of the test HEPA filter. The sampling system works well with particle counters fitted with relatively weak fans to draw in samples for counting; this is achieved by connecting the sampling system to both the inlet and exhaust outlet of a particle counter.

Description

GOVERNMENT INTEREST[0001]The invention described herein may be used, manufactured, and licensed by or for the United States Government.FIELD OF THE INVENTION[0002]This invention relates to a high flow rate self-calibrating aerosol dilution device, and a sampling system for providing particulate samples to a particle counter. The invention can be used for testing High-Efficiency Particulate Air (HEPA) filters by collecting samples up and downstream of the HEPA filter under test and comparing upstream and downstream sample counts.BACKGROUND OF THE INVENTION[0003]As noted in U.S. Pat. No. 7,536,898 issued to Owen, when particle counters measure aerosol concentrations above their operating range, the detectors can become saturated or exhibit undesirable nonlinear behavior. The drawback from these measurement devices arises when they are used to measure aerosol concentrations above the instrument's dynamic range.[0004]To overcome this obstacle, dilution techniques have been employed wher...

AI Technical Summary

Benefits of technology

The patent describes a system for testing the efficiency of a HEPA filter by using a dilution and sampling system. The system includes a test portion and a calibration portion, which helps determine the dilution ratio of the system, allowing for accurate particle counting. The sampling system collects samples upstream and downstream of the HEPA filter, allowing for accurate counts even when using new generations of particle counters. The system also includes a flow rate balancing system to ensure accurate counts. The technical effect of the system is to provide a reliable and accurate method for testing the performance of HEPA filters in laboratories and clean rooms.

Problems solved by technology

As noted in U.S. Pat. No. 7,536,898 issued to Owen, when particle counters measure aerosol concentrations above their operating range, the detectors can become saturated or exhibit undesirable nonlinear behavior.

The drawback from these measurement devices arises when they are used to measure aerosol concentrations above the instrument's dynamic range.

It is often difficult to determine the dilution factor accurately, leading to inaccurate and disputed counts.

Consequently, such counters are easily overwhelmed if exposed to high particulate counts.

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